The answer to this question would be 5 by 9.
Took me a minute to think.
Form ratios.
x, the small triangle, forms a ratio with 6, the big triangle.
The part of the side that is equal(with the dash) that is part of the small triangle
is equal to 6-x, the big triangle.
Yes, you can cross-multiply here!

<em>Now,</em><em> </em>cross multiply.
P.S. Use distributive property.
36-6x = 8x
Add 6x on both sides.
36=14x
Divide by 14 on both sides.
x =

=
Check the picture below.
now, keep in mind that ship B is going at 20kph, thus from noon to 4pm, is 4 hours, so it has travelled by then 20 * 4 or 80 kilometers, thus b = 80.
whilst the ship B is moving north, the distance "a" is not really changing, and thus is a constant, that matters because the derivative of a constant is 0.
We use P = i•e^rt for exponential population growth, where P = end population, i = initial population, r = rate, and t = time
P = 2•i = 2•15 = 30, so 30 = 15 [e^(r•1)],
or 30/15 = 2 = e^(r)
ln 2 = ln (e^r)
.693 = r•(ln e), ln e = 1, so r = .693
Now that we have our doubling rate of .693, we can use that r and our t as the 12th hour is t=11, because there are 11 more hours at the end of that first hour
So our initial population is again 15, and P = i•e^rt
P = 15•e^(.693×11) = 15•e^(7.624)
P = 15•2046.94 = 30,704